1. Field of the Invention
This invention relates to gang plows whether of the rollover type or not and having a variable width, that is, plows in which the transverse spacing between furrow-cutting lines or so-called lines of action of two adjacent plow bottoms is adjustable in order to obtain a correspondingly variable furrow pitch.
Plows of this type are provided in known manner with a beam which is inclined with respect to the direction of forward travel of the tractor and which carries a plurality of plow bottoms maintained in uniformly spaced and parallel relation by means of a device of the deformable parallelogram type.
Adjustment of the furrow pitch is obtained on the one hand by modifying the common angular position of the plow bottoms with respect to the plow beam and on the other hand by modifying the angular position of the beam with respect to the tractor in order to ensure that the lines of action of the plow bottoms are aligned with respect to the direction of forward travel.
The plow beam is supported at the rear end by a wheel which bears on the ground and at the front end, through a forecarriage unit, by the link-arms of the tractor "three-point hitch" system. In the case of a rollover plow, the beam is capable of undergoing a pivotal displacement through an angle of 180.degree. about a longitudinal axis with respect to the forecarriage unit.
The double problem encountered in gang plows lies in the fact that, on the one hand, the furrow-cutting lines or so-called lines of action of the plow bottoms must be parallel to the direction of forward travel while plowing is in progress and after or during adjustment of spacing of said lines of action and that, on the other hand, the line of action of the foremost plow bottom must be positioned relative to the tractor such that its furrow will be located with respect to the furrow cut during the previous trip at a distance equal to the new furrow spacing.
2. Description of the Prior Art
This problem can be solved by using two hydraulic cylinders for setting the cutting width and for transversely displacing the support beam of the plow bottoms as is shown in U.S. Pat. No. 4,186,806. This has proven to be a satisfactory solution, however, the two hydraulic cylinders along with the necessary conduits and controls add considerably to the cost of that system.
Another satisfactory solution, has been proposed by the Applicant in his pending U.S. patent application Ser. No. 290,903 filed Aug. 7, 1981, now U.S. Pat. No. 4,415,040, which application is by reference hereby made a part of this application.